The present invention relates to a transport apparatus for perforated objects such as perforated circuit boards. More particularly, the present invention relates to a transport apparatus for removing perforated objects from a stack of such objects.
Frequently in the electronics industry, a circuit board must be removed from a stack of such boards and conveyed to a work station for further operations or installation. Automated devices are normally employed for this purpose. One type of automated device used for this purpose includes a vacuum operated gripper head which removes the top circuit board from the stack by means of suction. In the case of perforated circuit boards, however, difficulties often arise due to the tendency of such suction-operated gripper heads to lift more than one circuit board from the stack.
It is sometimes possible to reduce the tendency of the gripper head to lift more than one object by adjusting the suction power of the gripper head so that the weight of only a single circuit board will be supported. Adjustments of this type, however, must be highly accurate and, when possible, require expensive control devices. Furthermore, the transport device would require delicate adjustment whenever the type of circuit board being transported is changed.
Vacuum-type gripper devices are shown, for example, in U.S. Pat. No. 2,880,030, German Pat. Nos. 850,797, 3,009,580, and Japanese Laid-Open Patent Publication No. 57-145723. Additionally, German Pat. No. 1,756,327 relates to a device including a suction gripper for loading and unloading pallets. The side of the gripper which faces the pallets is closed off by a plate provided with orifices, with the center area of the plate having a dense area at the bottom of which an elastic sealing element is located. The dense area seals potential gaps between a plurality of pallets to be lifted to prevent loss of suction.
The present invention is an improvement over previous suction-operated transport devices. More particularly, the present invention simply and economically overcomes the undesirable tendency of known transport devices of removing more than a single circuit board from the top of a stack of perforated circuit boards.